industry wide bandgap technologies
Kyma eyes new opportunities
Diversification lies at the heart of Kyma Technologies’ vision for its future. It first made a name for itself as a leading supplier of wide bandgap materials, but it is now expanding its offerings and has started to provide plasma vapour deposition (PVD) equipment and photoconductive switches, explains the company’s chief executive officer, Keith Evans.
W AlN templates
The first of these, our AlN templates, consist of a thin layer of this crystalline wide bandgap material, grown on either sapphire or silicon. AlN deposition is carried out with a patented, proprietary
hen you hear the name Kyma Technologies, I bet you think of bulk GaN. But that’s not the
only product developed by our team at Raleigh, NC. In addition to being a provider of high-quality HVPE-grown GaN materials, we offer a diverse and growing portfolio of products, including materials, equipment and devices.
Three of our most important product offerings are discussed in this feature: AlN templates for LEDs and power electronics; PVD crystal growth systems for fabricating AlN templates; and a novel, photoconductive GaN switch for optically isolated, rapid switching at high powers.
process called PVDNC - PVD of NanoColumns. This creates AlN crystalline layers with a defined nanostructure, consisting of a very dense array of AlN nanocolumns with a dislocation density that is very low – and possibly zero. According to atomic force microscopy and cross-sectional transmission electron microscopy measurements, the typical diameter of these nanocolumns ranges from 40 nm to 80 nm, and they have a very smooth surface with low root-mean-square roughness. Between the nanocolumns, which are oriented along the c+ axis, the AlN is of lower crystalline quality.
We routinely deposit our AlN nanocolumns on both flat and patterned sapphire substrates. The AlN templates that result enable our customers to form GaN with higher quality earlier in the buffer layer than they would get if they used just sapphire. Realizing a better buffer earlier brings two major benefits: Producers of epiwafers and devices can thin their GaN buffer, saving time and ultimately bosting throughput and reducing cost; or engineers can maintain the thickness of the buffer, leading to a lower defect density in the buffer and device active regions.
Our collaborators at John Muth’s group at North Carolina State University (NCSU) have documented the improvement in thermal conductivity in GaN as the defect density is reduced. That means that our PVD AlN template customers attain higher thermal conductivity GaN buffer layers faster during their buffer layer growth. Since the device active region for most devices replicates the structural quality of the top portion of the buffer layer, we can conclude that the entire device wafer and especially the device active region has lower thermal impedance, always a desirable attribute for a device epiwafer. The higher thermal conductivity of the GaN buffers and device active regions resulting from our AlN templates have enabled our customers to report higher LED yield and better device performance.
4-inch,6-inch and 10-inch diameter AlN on sapphire templates produced by Kyma Technologies using its patented and proprietary PVDND technology
62
www.compoundsemiconductor.net March 2013
It wasn’t obvious that our PVDNC process would work on patterned sapphire. However, it shouldn’t be that surprising that it does. After all, although today’s patterned sapphire substrate topologies contain micron or many-micron sized features, they
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143